<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>


  <script>

    let week_day = prompt('想查哪天呢？')

    switch (week_day) {
      case '星期一':
        alert('monday')
        break
      case '星期二':
        alert('Tuesday')
        break
      case '星期三':
        alert('Wednesday')
        break
      case '星期四':
        alert('Thursday')
        break
      case '星期五':
        alert('Friday')
        break
      case '周六':
        alert('Saturday')
        break
      case '周日':
        alert('Sunday')
        break
      default :
        alert('请输入真确的日期')
    }
  </script>
</body>

</html>